In order to direct a flying object, such as a missile, to its intended destination more steadily and accurately, the flying object's control surfaces (also commonly referred to as wings or tailfins) must be deployed from their stowed or launch positions and then locked into their fully opened or deployed positions. The current state of the art for such locking typically employs five basic types of mechanisms. However, all of the five types suffer from serious drawbacks.
The first type of mechanism uses a plunge pin contained in the fin base portion that extends into the rotating fin body as the fin rotates to reach its deployed position. This has proven to be robust in operation but expensive to manufacture and assemble, since it requires a relatively thick fin base portion to contain the plunge pin mechanism, multiple machining operations using precision jigs to produce the mating plunge pin holes in the fin and careful assembly where each fin assembly is shimmed individually to tight tolerances to ensure that sections of the plunge pin hole are properly aligned.
The second type of mechanism utilizes tapered protrusions on fin lugs that engage matching slots in the stationary lugs that reside on the body of the flying object. This locking mechanism yields solid and robust fin locking but the tapered protrusions are difficult and expensive to produce. Further, the required axial translation of the fin demands a large compression spring to ensure reliable operation. Additionally, the entire locking process is slow.
The third type uses a flexible plate attached to the rotating fin that snaps over a lug on the object body. The mechanism requires precision adjustment, dictating that each fin be adjusted individually and tested during assembly of the flying object. If the plate is too tight, it impedes deployment of the fin and if it is too loose, it fails to lock tightly.
The fourth type uses a separate locking piece with a tapered slot that engages a matching protrusion machined on the face of the rotating fin lug. The locking piece cannot rotate against the object body, so the fin motion is arrested when the lock engages the fin lug. The required tapered protrusion on the inside face of the fin lug is difficult and expensive to fashion.
The fifth type of locking mechanism forces the fin axially aft onto a machined cut in the aft stationary fin lug. This requires translation of the entire fin in order to operate. The resulting engagement of the lock is slow and multiple fin rebounds are sometimes encountered during flight of the object before the lock engages successfully.